We have investigated the degradation phenomena due to stresses such as gate bias application and visible light illumination as well as the ultraviolet (UV) exposure effects in amorphous silicon (a-Si) thin film transistors (TFT'S). The device parameters of the a-Si TFT, such as threshold voltage, field-effect mobility, and subthreshold slope, have been degraded by the bias stress and the vigible light illumination. Furthermore, we have found that the degradation in the a-Si TFT's are accelerated by multiple effects of the two stresses. However, the device characteristics of the a-Si TFT's are substantially improved by UV irradiation. Especially, after UV exposure, the off-current of This result may be the TFT's decreases remarkably while the on-current changes very little. attributed to an annealing effect on the dangling-bond defects in the a-Si layer of the TFT channel due to a number of phonons generated by the absorption of high energy UV phonons.
Amorphous silicon TFTS (a-Si TFTs) have been investigated by the atmospheric pressure CVD (APCVD) method using disilane. The deposition rate of a-Si was higher than 15 nm/min at 420 ℃. The field effect mobility and the on/off current ratio were higher than 0.38 cm^2/Vs and 10^4, respectively.
The merits of AMLCD technology for avionic displays in terms of visual, technical and economic characteristics are itemized. Detailed review of the advantageous visual characteristics obtained under high ambient illumination utilizing this method are presented. Details are also presented on a new, high-mobility, low temperature active-matrix process as developed by Litton. This new method offers a low-cost, highly producible process.
In this paper we present the electro-optical data on a series of liquid crystal mixtures, designed for low- to medium multiplexed Super Twisted Nematic (STN) displays (i.e. multiplex rates from 1:16 to 1:160). The liquid crystal mixtures have the following characteristics: 1) The mixtures are two-bottle systems in Δn. This ensures a large flexibility for choosing the cell gap and desired twist angle. 2) The threshold voltages range from around 2 V down to approximately 1 V (for 220°twist cells). This facilitates the choice of the proper liquid crystal mixture for a certain desired battery voltage. The relevant physical properties of the liquid crystal mixtures will also be presented.
By considering real optical properties of polarizers and birefringent films and using both analytic and numerical methods, we have carried out computer simulation for optimum design of FSTN-LCDs. From the simulation, we have obtained the optimum values of main parameters for good quality FSTN-LCD in the cases of Δnd=0.65, 0.75, 0.85, 0.95μm of liquid crystals and analyzed the And dependence of optical properties.
We studied the crystallization of a-Si by lamp annealing and the application of these poly-Si to the fabrication of TFTs. We found that the crystalline volume fraction and the grain size are larger for the poly-Si made using CVD a-Si compared with that using conventional PECVD a-Si from the X-ray and UV reflectance measurements. The surface crystalline volume fraction of poly-Si film by lamp annealing is over 80%. Using this poly-Si layer, we have made staggered type TFT on glass plate with field effect mobility of about 8 cm^2/Vs and the threshold voltage of less than 5V.
The effective channel length and series contact resistance were extracted for various thin film transistors. The series contact resistance was decreased with source-drain voltage, and the difference between mask channel length and effective channel length was decreased with the source-drain voltage. For small source-drain voltages, both of them came to be constant. Contact-series resistances were measured for various shapes of thin film transistors to see geometrical effect.
Polysilicon TFTS With different channel dimensions were fabricated on low-temperature crystallized amorphous silicon films and as-deposited polysilicon films. The performance of these devices was investigated and compared. The performance of devices fabricated on annealed amorphous silicon film is shown to be superior to that of devices fabricated on as-deposited polysilicon films. It was found that the performance of polysilicon TFTS depends strongly on the material characteristics of the polysilicon films, but only weakly on the channel dimensions.
The seed assisted crystallization process has been studied and compared with the conventional SPC process. The micro crystalline and the poly crystalline seed layer were prepared as thickness of 100Å- 500Å and a-Si:H was deposited on the seed layer. They were crystallized by furnace annealing at N, atmosphere. TEM micrographs and Raman Spectra were used for analyzing the crystalline quality. It suggested a new possibility of the low temperature crystallization process.
In this paper, the design sensitivity analysis is introduced to find optimum coil distributions that minimize both the convergence and distortion errors for the magnetic deflection system with large-angle. The design sensitivity coefficients are numerically computed by using the centered difference method. Volume integral equation method with magnetization vector M^^→ as unknown variable and 4th order Runge-Kutta method are used to compute the distributions of magnetic induction and the electron beam trajectories, respectively. Through the numerical example with 110° deflection system for the screen of 29", the usefulness of the alrorithm is verified.
This paper presents a model which predicts the effects of banding application to TV glass bulb under vacuum stress. Though the bend is wrapped around the periphery of the panel, the pressure is found to apply only over corner area. Automatic finite element mesh generation program BULB-3D is used, and the analysis is done by general purpose S/W ANSYS. The reuslt is verified using recovery data which are used in customer's process, and is found to agree within 3% error. As a result of banding parameter variation, it is found that there exists an optimum value of force which maximizes the stress reduction. The banding height should be as high as possible to reduce the stress.
The ten major requirements for all electronic information displays will be analyzed and discused in each of four fundamental categories: Readability, addressability, utility, and cost. A display approach must possess credible performance in each of the ten major requirements. If it does not, then it should be corrected through further research before the development of the display approach can logically continue. These ten items can serve as a checklist to determine if a display approach is worthy of further development. They can also serve as criteria for comparing different display approaches and design options.